Cap seals are materials structured to cover an unsealing part of a container, such as a bottle, and the vicinity of the unsealing part. Such an unsealing part specifically includes an opening at an end or other location of the container, and a cover or a stopper closing the opening. Cap seals are formed, for example, of a shrink film that shrinks when heated. Such a cap seal protects the peripheral portion of the opening from impact, prevents entry of external air into the container, or indicates that the container is not yet opened. Recently, there has been proposed a cap seal provided with an IC tag to manage or authenticate the commodity product which is constituted of a container and the contents. Commodity products provided with such cap seals are managed or authenticated through reading of information recorded on the IC tags using contactless communication (e.g., see PTL 1).